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		| abm.ben 
 
 
 Joined: 02 Sep 2008
 Posts: 4
 
 
 
			    
 
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				| Problème - AD7711 |  
				|  Posted: Tue Sep 09, 2008 7:50 am |   |  
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				| Hello everyone! 
 I wish to make a system to acquire the temperature with a Pt100, to be made with an AD7711 interfaced with a PIC 18F258.  I used the driver
 "AD7710" provided on the topic,
 http://www.ccsinfo.com/forum/viewtopic.php?t=28553&highlight=ad7710
 
 I have made a test that did not go correctly.  It gives me values which I
 cannot interpret:
 
  	  | Code: |  	  | -Pour  10°c  .... SDATA=0x810DF3
 -Pour  40°c  .... SDATA=0x812BB9
 -Pour  120°c .... SDATA=0x817AE0
 -Pour  140°c .... SDATA=0x82651E
 
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		| FvM 
 
 
 Joined: 27 Aug 2008
 Posts: 2337
 Location: Germany
 
 
			    
 
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				|  Posted: Tue Sep 09, 2008 12:59 pm |   |  
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				| I guess, you noticed that the AD7711 has some programmable features, that must be enabled for Pt100 measurement, particularly exitation current. Also a higher gain than 1 is most likely meaningful. This doesn't require a new driver, just setting the respective control register bits. 
 I would also expect, that you did some precalculations, what should be a meaningful measurement in your application. We don't know either your exact circuit nor possible different control register settings already implemented and thus can't know, what may be a right or wrong measurement.
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		| abm.ben 
 
 
 Joined: 02 Sep 2008
 Posts: 4
 
 
 
			    
 
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				|  Posted: Wed Sep 10, 2008 6:45 am |   |  
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				| Thank you for your answer very fast. 
 what I have done is use the driver provided on the topic and put a resistor precision instead of pt100 and depending on the value returned I made the calculated temperature via an equation correct and well validated.
 
 for everything that is setting the record control I have already changed the gain, activating the flow of excitement, but whenever the return values are wrong.
 
 there is something that I did not understand in the driver provided on the forum is that in fact what the return record SDATA east of 32bit data while it would just over 2 bytes.
 
 if your already succeeded in doing that. can have them communicate.
 
 thank you.
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